This invention concerns induction hardening which is widely used in industry to harden such parts as cam shafts, crank shafts, etc. In this process an inductor surrounds a section of the part, and a high frequency voltage is applied to the inductor. This induces a current in the surface of the part (to a variable depth set by design), rapidly heating the same to a desired temperature. A flow of quenching coolant is then directed at the part, thereby hardening the surface of the part to the hardness and depth desired.
In the conventional arrangement, the inductor (typically a single turn coil) is constructed in two halves in order to allow positioning of the part within the coil by a clam shell opening of the inductor closed around the part when the ends of each half are pivoted together. The coil halves can also be separated by linear motion and then brought together to surround the part. In this arrangement it is necessary to make an electrical connection between the inductor half coil ends in order to complete the circuit and cause current to flow through both coil halves.
Power from a high frequency power source is applied to the inductor to cause a high frequency current to flow through the connected inductor coil halves.
Such electrical connections must be made with care to insure a proper flow of power through the complete inductor coil, slowing the process of loading the part. Such connections are subject to wear and present a maintenance burden in this application. This requirement makes automation of part loading somewhat impractical.
Another problem often encountered is the formation of gaps in the electric field induced around the inductor which would create unevenness in the hardening obtained in the part, necessitating rotation of the part in the inductor coil in order to prevent this, complicating the equipment needed and slowing the completion of the hardening part heating cycle.
It is an object of the present invention to provide an arrangement and method of powering an inductor formed of two half coils which does not require the making and breaking of an electrical connection between the two inductor half coils.
It is a further object of the invention to provide such arrangement and method which does not create gaps in the electrical field created by the inductor coil to and thereby not require any rotation of the part during the induction hardening process.